Method and apparatus for detecting defects in lenses

ABSTRACT

There is provided a method and an apparatus for testing an optical component for cosmetic defects, the component having optical surfaces, a peripheral surface and a bulk defined by the optical and peripheral surfaces, a range of inspection of the component including at least one optical surface and the bulk of the component at least in the vicinity of the one optical surface. The method includes producing at least one beam of inspection radiation and directing rays of the at least one beam onto the peripheral surface at such angles as to enable the rays to travel in the bulk of the component by multiple total internal reflections from the at least one optical surface, providing illumination of each point in the inspection range by set of rays at different angles, and to emerge from the component through the peripheral surface, and monitoring a radiation scattered by the defects and emerging from the component through the at least one optical surface, thereby identifying the defects.

FIELD OF THE INVENTION

This invention relates to a method and apparatus for detecting defectsin optical components such as lenses, particularly cosmetic defectsconsisting of surface flaws and occlusions.

BACKGROUND OF THE INVENTION

Optical components of transparent material, for example, opticalophthalmic lenses, must be tested for defects prior to theirutilization, particularly for surfaces flaws such as scratches, smears,cracks, chips, stains, and for occlusions such as bubbles or streaks.Limit values of tolerable flaws are established in internationallyrecognized standards for precision optics, specifically DIN 3140 orMIL-0-13830 or less stringent standards used by the ophthalmic industry,such as DIN 58203.

Conventionally, the testing is carried out by visual inspection bytrained personnel, mostly in a darkened room. Such a procedure isexpensive, not sufficiently objective and not sufficiently reliable.Therefore, efforts are being made to develop methods and devices for theautomatic and objective testing of optical components.

DE-OS 2337597 discloses a test method according to which a light ray isfocused on the surface of the optical component to be tested and issequentially moved over said surface, while being kept in focus.Illumination of the object to be tested is, in this case, achieved inthat the test piece rotates on its axis and the impinging light ray isslowly radially deflected in such a way that it describes aspiral-shaped pattern on the test piece, whereby its state of focus mustbe continuously readjusted according to the curvature of the surface tobe scanned. The light which penetrates the component is reflectedbackwards, passes once again through the component, and then impinges ona detector. The deviations in the intensity of the signal received makeit possible to deduce a flaw and to localize it. Such a method, however,requires very expensive devices for carrying it out. Furthermore, saidmethod does not allow to differentiate between surface flaws and dust orwater marks on the surface of the component.

German Patent Application No. 3620108 describes a method according towhich the optical component to be tested is rotated on its axis and isilluminated by a light beam which is displaced along the diameter of thecomponent at a frequency greater than the angular rotation speed of thecomponent, whereby a spoke-shaped pattern is generated. This patternmoves once through the component when the same is turned by 360%, and inthis way uniformly illuminates each point of its volume with light inapproximately the same state of focus. The radiation, the normaldiffusion of which is disturbed by any possible flaws in the surfaces ofor inside the component, is detected in the post-installed testingsystem and only the light diffracted by flaws in the component Is usedto produce the image. A device operating in this way is expensive andthis method does not differentiate between dust or water marks and flawsof a component.

DE-OS 3237511 discloses placing the optical components to be tested inthe optical path of a television camera and displaying through thecomponent a test pattern on the camera. The disturbances caused by flawsin the component produce a video signal which deviates from a controlsignal that is not influenced by the component. The deviations betweenthe control signal and the actual signal received permit to identify theflaws. By this method, however, smaller flaws, such as those resultingfrom scratching, smears or hairline cracks, cannot be detected, and itis impossible to differentiate dust or water marks from surface flaws.

DE-OS 3011014 attempts to increase the sensitivity of the aforesaidtesting procedure by suggesting that the component to be tested beilluminated completely, a television image be produced, and flaws bededuced by line-for-line analysis of the video signal. Such a procedureis complicated, expensive, not sufficiently accurate, and does not allowto differentiate dust and water marks from flaws or occlusions.

U.S. Pat. No. 3,988,068 discloses a method for detecting cosmeticdefects in lenses, where in order to distinguish between actual defectsand surface dust, it is suggested to direct a light into the lensthrough its peripheral edges so that the light will impinge upon thefront surface at angles more than critical angle to undergo one totalinternal reflection within the lens and leave the lens though its edge,and to detect a light scattered by any of the defects. It is mentionedin the patent that for this purpose the light sources should be alignedrelative to a front surface of the lens, which alignment may be "easily. . . accomplished with slight amount of experimentation". However,there is not a single hint in the patent how to provide such alignmentor according to which requirements it should be accomplished. Neither itis mentioned how to avoid emerging of light, which travels within thelens in a non-controllable way, through inspected surface and how toavoid the illumination of the non-finished surface by the non-controlledillumination light. Moreover, the disclosed method is not effective asit clearly cannot provide for sufficient detection capability seeingthat the light from each illumination source illuminates each defectunder an extremely narrow range of angles thus decreasing a possibilityof the scattered light to reach the detection means and consequently itsdetectability. Furthermore, the illumination of the inspected surfaceand bulk of the lens is not homogeneous influencing the sensitivity ofthe method. In addition, it is very important in this method for theedge of the lens to be of good quality and this requirement alsorestricts applicability of the method.

SUMMARY OF THE INVENTION

It is the purpose of the present invention to provide improved, morereliable and less complicated and expensive method and apparatus fortesting optical components for cosmetic defects.

Other purposes and advantages of the invention will become apparent asthe description proceeds.

In the further description and claims the term "sagittal plane of theoptical component" means a plane in which the central line of theoptical edge lies; generally, when the component is laid on a flatsurface, the sagittal plane is parallel to the surface. The term"meridional plane" means a plane containing the optical axis of thecomponent and chief rays of illumination radiation; generally said planeis perpendicular to the plane of the edge (sagittal plane). The term"optical surfaces" refers to those optical surfaces of the inspectedcomponent which may be crossed by a directed light when the component isin its normal use. By the "range of inspection" is meant herein aportion of the optical component in which the cosmetic defects will beidentified in each application of the present invention.

In accordance with the present invention, there is provided a method fortesting an optical component having optical surfaces, a peripheralsurface and a bulk defined by said optical and peripheral surfaces, forcosmetic defects in a range of inspection including at least one saidoptical surface and said bulk of the component at least in the vicinityof said one optical surface, said method consists of producing at leastone beam of inspection radiation and directing rays of said at least onebeam onto said peripheral surface at such angles as to enable the raysto travel in said bulk of the component by multiple total internalreflections from said at least one optical surface, providing each pointin said inspection range to be illuminated by set of rays at differentangles, and to emerge from said component through said peripheralsurface, and monitoring a radiation scattered by said defects andemerging from the component through said at least one optical surface,thereby identifying said defects.

It is known that a light beam propagating in a medium with a refractiveindex n (n>1) will be totally internally reflected from an interfacebetween the medium and the air (n=1) if an angle of incidence of thelight beam on the interface is larger than the critical angle "γ":

    γ=arc sin (1/n),

Therefore, in order to provide radiation propagation within atransparent optical component by multiple total internal reflections, itis necessary to keep the angles of incidence of its beams on opticalsurfaces of the component larger than the above critical angle. However,with a variety of shapes of optical and peripheral surfaces of theoptical components such as lenses, the above requirement may befulfilled only by means of a specific way of introducing the inspectionradiation into the component which is defined by the set of angles atwhich the radiation beams should be introduced into the component and aposition at the peripheral surface of the component where each radiationbeam enters the component. Thus, in the preferred embodiment of thepresent invention directing of the at least one beam of said inspectionradiation includes forming and orienting said beam substantially in themeridional plane of said component, and scattering said beamsubstantially in the sagittal plane of said component.

Thus, method, in accordance with the present invention, allows tocontrollably illuminate different kinds of optical components andprovides an effective inspection of finished lenses, in which case therange of inspection includes both optical surfaces and said bulk of thecomponent, as well as of semi-finished lenses, where the range ofinspection includes a finished surface of the component and the portionof its bulk adjacent to the finished surface, the size of this portiondepending upon the thickness of the semi-finished lens.

For a finished optical component with mutually parallel surfaces, suchas optical plates and/or "plano" lenses, the inspection radiation may beinserted via all points of the the edges of the component at allpossible angles α, when the edge of the optical component constituteswith its optical surfaces an angle δ (in degrees) which is more than 2γ.

However, if the optical surfaces of the component are inclined withrespect to its edge at the angle δ which does not comply with the abovecondition, the illumination radiation may be inserted into the componentvia its edge at any angle α which satisfies the following condition inthe meridional plane of the optical component (see FIG. 1a):

    -90<α<arc sin cos(δ+ε)                 (1)

here ε=90-γ.

For different negative finished lenses precise values of insertionangles may be obtained by regular ray tracing calculations. However,these values may be approximately estimated by means of relation (2)given below for negative lenses with their diameter 2r, centralthickness t_(o), peripheral thickness t_(r) and with curvature radii R₁and R₂ and β₁,2 =arc sin (r/R₁,2) (FIG. 1b). Relation (2) providesprecise values for insertion angles for lenses with t_(r) /r<<1. In thiscase the inspection radiation will not leave the

    n sin{[β.sub.1 +[x(β.sub.2 -β.sub.1)-εt.sub.o ]/t.sub.r }<sinα<n sin{β.sub.1 +[x(β.sub.2 -β.sub.1)+εt.sub.0 ]/t.sub.r }               (2)

The relation (2) provides precise values for insertion angles for lenseswith t_(r) /r<<1. In this case the inspection radiation will not leavethe component through its optical surfaces, if the insertion angle γsatisfies the condition (1) and the requirement (2).

For biconcave lens R₁ and, consequently, β1 are negative values.

For all types of positive lenses with diameter of zone to be inspected2p, the inspection radiation may be inserted via the edges of the lens,subject to condition (1), and through portions of their optical surfacesout of zones to be inspected at any angle θ which satisfies the nextcondition (3) in the meridional plane (see FIG. 1c):

    θ.sub.1,.sub.2 <arc cos(n sin[arc sin(R.sub.1,.sub.2 /an)-arc sin(Lρ/aR.sub.1,.sub.2)])                             (3)

where L=R₂ +t₀ -R₁, ##EQU1## the sign "+" and index "1" are to be usedfor determination of insertion angle through a convex surface of thelens, the sign "-" and index "2" are to be used respectively for itsconcave surface.

In case when a semi-finished lens is to be inspected, conditions shouldbe provided for the illumination radiation to travel by multiple totalinternal reflections through a part of a bulk of the semi-finished lensadjacent to the finished surface without reaching the non-finishedsurface and a suitable range of insertion angles α should be calculated.For a semi-finished lens with diameter 2r, radius of the finishedsurface curvature R and minimal thickness t, the illuminating radiationmay be inserted in an arbitrary point of its edge at a distance x fromthe finished surface (see FIG. 1d) at any angle in the following range:

    arc sin(n sin(β-Δφ))<α<arc sin(n sin(β+Δφ))                                 (4)

here β=arc sin(r/R), Δφ is determined in implicit form by the nextexpression:

    Δφ=arc cos{(R-t)/[R-x cos(β-Δφ)]} (5)

The range of insertion angles a should be reduced by up to 4 degrees toprovide compensation for scattering by the edges, if any.

In accordance with the present invention there is also provided anapparatus for performing the above method consisting of

means for supporting the component to be tested;

illumination means for producing at least one inspection radiation beam;

means for conveying said at least one beam to a peripheral surface ofthe component including optical means for forming said at least one beamin a meridional plane of the component and for orienting said at leastone beam in said meridional plane of the component so as to enable raysof said at least one beam to travel in a bulk of the component bymultiple total internal reflections from at least one optical surfaceand to emerge from said component through its peripheral surface, andmeans for scattering said at least one beam in a sagittal plane of thecomponent about its peripheral surface so as to provide said radiationwith a substantial divergence in said sagittal plane;

means for receiving radiation, If any, emerging from the opticalsurface;

means for analyzing said radiation, thereby identifying said defects;

light protection means to avoid a non-controlled illuminating of thecomponent.

In one preferred embodiment the inspection radiation consists of onebeam, e.g. a laser beam, with a ring-shaped cross-section in a planesubstantially parallel to said sagittal plane. In this case theapparatus further includes reflecting means for forming and orientingsaid beam and directing the beam through said scattering means to theperipheral surface of the component.

In another perfected embodiment, the inspection radiation consists of anumber of beams which are introduced into the component at a number ofzones along the peripheral surface of the component. In this case thebeams may be provided either by dividing one beam from one radiationsource, e.g. by means of optical fiber bundles, or by a plurality ofindependent radiation sources each of which produces one or more beams.Preferably, the radiation sources are arranged in a number of ringssubstantially parallel to said sagittal plane of the component and areadapted to controllably produce said radiation beams.

Preferably, the conveying means may include a combination of eitherreflecting and screening means or at least one lens and refractionoptics, however other different suitable combinations may be employed.

In the preferred embodiment of the present invention, the radiationscattered by the defects and emerging from said component through saidat least one optical surface is monitored by producing therefrom animage of complete lens or part of the lens, e.g. by means of ahigh-resolution TV camera with a lens having large depth of focus can beused for examination of both optical surfaces and bulk of the lenses.The image is transferred to a computer via a frame grabber to identifythe defects of the component and to classify it by means of dedicatedsoftware. The image processing system analyzes the said image to detectthe presence of a defect, its location, dimensions and type (dig,scratch, etc.). However, different monitoring and analyzing systems maybe used.

Proper means are to be used to avoid non-controlled illumination of theinspected optical surfaces.

BRIEF DESCRIPTION OF THE DRAWINGS

For a better understanding, the invention and its further preferredfeatures will now be described, by way of example only, with referenceto the following drawings in which:

FIGS. 1a, 1b, 1c and 1d are sketches schematically illustratingconditions at which inspection illumination is introduced into differentkinds of inspected components, according to the present invention;

FIG. 2 is a schematic representation of an apparatus according to theembodiment of the invention;

FIG. 3 is a schematic view of a component being inspected and parts ofthe apparatus holding and illuminating it, according to the embodimentof the invention, seen in a plane parallel to the sagittal plane of thecomponent;

FIGS. 4 and 5 are schematic illustrations of the mounting of a componentto be inspected, of the means for introducing inspection radiation intoit, of a paths of radiation rays within the component and of itsscattering by the component imperfections;

FIGS. 6, 7, 8 and 9 are schematic illustration of the alternativeembodiments of the present invention.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

FIG. 2 illustrates one embodiment of an apparatus for inspection of anoptical component 20 in accordance with the present invention. Theapparatus consists of an illuminating means, generally designated as 1,image acquisition means, generally designated as 2 and image processingmeans, generally designated as 3.

The illuminating means 1 includes a radiation source 10 and conveyingmeans including a forming and orienting component 17. Generally, theradiation source may be of any desirable kind. In the preferredembodiment it is designed using an injection laser diode functioning atan operational wavelength of 790-870 nm and followed by a concentratinglens 11 and a trifurcated optical fiber bundle, generally designated as12. Alternatively, the radiation source may be represented by a numberof independent radiation sources, it being only necessary that a numberof radiation beams be generated and be available for testing thecomponent. As shown in FIG. 3, the fiber bundle is divided into threebranches 13 providing three radiation beams, but they may be in adifferent number, e.g. less or more than 3. The outputs of the fiberbundle may be preferably adjusted by displacing them parallel to thecomponent radius (radial displacement) and/or parallel to the componentaxis "A" (axial displacement).

In the described preferred embodiment the forming and orientingcomponent 17 provided for each beam comprises a beam forming lens 14, anorientating element 15 and a scatterer 16. The lens 14 is preferably apositive lens adapted to determine an initial angular distribution ofthe inspection radiation beam in the meridional plane of the opticalcomponent. The lens 14 may be designed as a spherical lens, or as acylindrical lens with its axis parallel to the edge of the inspectedcomponent. The lens 14 may be preferably adjusted by its radialdisplacement.

The orienting element 15 is in the form of a deflecting Fresnel prism,preferably designed as a section of a Fresnel prism with a variablydeflecting angle (Fresnel cylindrical lens) and is adapted to impart tothe illumination beam a desired orientation in a meridional plane of thecomponent. The Fresnel prism 15 is placed between the forming lens 14and the component 20 for deflecting the inspection radiation beam to thecomponent through its edge. The Fresnel prism may be preferably adjustedby its axial displacement.

The scatterer 16 is placed between the Fresnel prism 15 and thecomponent 20 and preferably designed as a lenticular, that is an arrayof optical surfaces consisting of many parallel cylinders with theiraxes parallel to the optical axis of the component 20. The scatterer isdesigned to form an extremely wide angle of divergence of radiation beamin a sagittal plane of the component 20, without affecting the beamangle distribution in its meridional plane. In the particular embodimentillustrated, each beam is scattered so as to cover 60° of the peripheryof the component.

In order to avoid a non-controlled illumination of the component 20 itis screened by a light protective enclosure 18.

In operation, each inspection radiation beam produced, formed, orientedand scattered, in accordance with the present invention, by therespective elements of the illumination means enters the component to beinspected and travels through it, by multiple total internalreflections. Whenever it meets any single irregularity and/or occlusionin the component 20, it will be scattered by it to form beams, whichemerge from the component through its optical surfaces, such as the oneschematically indicated as 21 in FIG. 2.

The image acquisition means 2 includes a high resolution TV camera 24having a lens 26 and a frame grabber 27. The beam passes to the lens 26within a light protecting connector 23, and through an optical filter19. The image produced by the camera 26 is transferred via the framegrabber 27 to the image processing means including computer 25, where Itis processed by means of a dedicated software.

An iris diaphragm 22, interposed in the path of the beam, defines anarea of interest and prevents the light, emerging from the edge of thecomponent, from reaching the lens 26 of TV camera 24.

FIGS. 4, 5 schematically illustrate how the inspection radiation isintroduced into the component and show paths of the radiation rayswithin the component.

In the embodiment of FIG. 4 the component 30 to be inspected is anegative meniscus lens having an edge 31 and an illumination beam isintroduced into the component through its entire edge 31. As it isexplained with reference to FIGS. 2 and 3, the radiation beam conveyedby the optical fiber bundle 13 passes through the lens 14, Fresnel prism15 and the scatterer 16. The inspected lens 30 is held by clamping ring32, 33 having jaws 34, 35, mounted in the support schematicallyindicated at 36, 37, which clamping ring permits to adjust the lensposition, relative to the illuminating means, by axial displacement ofthe lens 30.

FIG. 5 illustrates a positive meniscus lens 40 with an edge 41 and anillumination beam penetrates the lens 40 not only through its edge 41,but also through peripheral surfaces 42 and 43. Elements 14, 15 and 16may be essentially identical to the same elements of FIG. 3 and elements13, 32, 33, 34, 35, 36, 37 are the same as in FIG. 4.

Paths of the radiation beams within the component illustrated in FIGS. 4and 5 are similar, therefore only that of FIG. 5 will be furtherexplained. Thus, the lens 40 receives the radiation from the element 17through the lens edge 41 and its peripheral surfaces 42, 43. The path ofthe radiation is indicated by lines and arrows. It undergoes multipletotal reflections, but when it encounters an occlusion 44 or a surfaceimperfection 45, it is scattered out of the lens through the opticalsurfaces 46, 47.

FIG. 6 schematically illustrates an alternative embodiment of theinvention in which for illumination of the component 30 a number of wideangle radiation sources 51, 52, 53 mounted in concentric rings (only onesource of each ring being shown) is used, and for forming the radiationbeams and for imparting to them a desired orientation in the meridionalplane of the component, a forming and deflection mirror 54 is used incombination with screening rings 55, 56 and/or screening diaphragms 57,58. In the preferred embodiment the mirror 54 is designed as a toricalmirror or a number of torical or cylindrical mirror segments. Suitableinsertion angles of the illumination radiation beams are provided byproper disposition of the radiation sources 51, 52, 53 and of theoptical component to be tested 30 with regard to the forming mirror 54.To provide desired insertion angles of the inspection radiation suitablefor different optical components 30, the mirror 54 and screening rings55, 56 and/or diaphragms 57, 58 may be preferably adjusted. This may bedone by suitable axial displacing mirror 54 or component 30 and/or byradial displacing the mirror segments, axial displacing the screeningrings 55, 56 and/or diaphragms 57, 58, and/or by radial and/or axialdisplacing the radiation sources 51, 52, 53, and/or switching saidsources in any combination, the combination of which is chosen withrespect to the specifically used illumination of the component. Thescatterer 16 forming an extremely wide angle inspection radiation beamin the sagittal plane of the component may be used if the radiationsources divergence angle is not sufficiently wide.

FIG. 7 schematically illustrates an alternative embodiment of theillumination means for testing a component 40, wherein instead ofconcentric rings of the radiation sources one illumination beam 59 of aring shaped cross-section is used. In addition, for a more uniformillumination of the component to be tested 40, the forming mirror 54accomplished by screening rings 55, 56 and/or diaphragms 57, 58 andscatterer 16 is used. The beam is formed by means of suitable conveyingmeans, e.g. designed as a pair of two conical or pyramidal mirrors 61,62, as illustrated on FIG. 7, or by a properly designed optical fiberbundle. An appropriate adjustment may be provided by inclination and/orradial and axial displacement of mirror segments 54, axial displacingthe screening rings 55, 56 and/or diaphragms 57, 58 and/or mirrors 61,62.

The above preferred embodiments illustrated in FIGS. 6 and 7 may be usedfor the illumination not only of negative (FIG. 6) or positive (FIG. 7)meniscus but also of all types of lenses and substrates: semi-finishedlenses, "plano" lenses, positive and negative lenses of differentoptical power and of all kinds of ophthalmic lenses: single vision(spherical and torical), bi-focal, progressive, aspherical, etc.

FIG. 8 illustrates an alternative embodiment of the invention, suitablein particular for optical plates and "plano" lenses, in which forproducing the widest angles insertion of the illumination radiationreceived in a meridional plane of a component 60, a combination ofcylindrical or conical mirrors 63 with torical mirror 64 is used. Anarray of wide angle radiation sources is placed on the central plane Bof the torical mirror 64 at the position nearest to its surface and iscombined with a cylindrical or conical mirror 63 and torical mirror 64consequently reflecting a radiation beam 68 for insertion thereof intothe component 60. The use of screening rings 66, 67, similar to 55, 56in the previous embodiments, allows to control of an insertion angle ofillumination radiation in meridional plane by axial displacement of therings and enables inspection of optical component of different kinds.Due to the use of the cylindrical (conical) mirror 63 no additionalmeans am needed in the embodiment for spreading the illuminatingradiation in the sagittal plane.

FIG. 9 illustrates the embodiment of a simplest illumination arrangementfor inspection of semi-finished lens 70. A number of rings of narrowangle radiation sources 71, 72, 73 (only one source of each ring isshown) is directed to a finished surface 74 of the lens through its edge78 so as to provide multiple total internal reflections of the radiationfrom the surface 74 without illuminating a non-finished surface 75. Theradiation sources are combined with lenticular scatterers 76 essentiallyidentical to the element 16 in FIGS. 6-8. The width of the radiationinsertion zone is limited by a screening ring 77 and may be adjusted byan axial displacement of the ring. An appropriate adjustment of theincidence angle of illumination radiation is provide by switching thesuitable radiation sources 71, 72, 73.

In all the embodiments of the present invention the apparatus preferablyincludes also adjustable clamping rings with jaws made of soft,light-absorbing material, such as rubber, velvet, cloth, felt, etc., forstationary mounting of the component to be inspected and to avoidexterior propagation of the inspection radiation along the opticalsurfaces of the component. The rings are so designed that they may beadjusted to different diameters of the optical component and they mayadjust the position of the optical component relative to theilluminating apparatus along the axis of the component.

Thus, the present invention provides for the method and apparatusenabling such advantages as a possibility to check all kinds of lensesand substrates, particularly ophthalmic lenses, e.g. single vision(spherical, torical), bi-focal, progressive, aspherical, etc. andsemi-finished lenses, and differentiating between cosmetic defects of anoptical component, such as flaws and occlusions, on the one hand, anddust and water marks on its surfaces, on the other hand, Independence ofinspection from said dust and water marks, thereby allowing forinspection of optical components without requiring their prior cleaning.

While the present invention has been described by way of illustration ofits preferred embodiments, it will be understood that the invention isnot limited to them and may be carried into practice by persons skilledin the art with many variations, modifications and adaptations, withoutdeparting from its spirit or exceeding the scope of the claims.

The invention claimed is:
 1. Method for testing an optical component forcosmetic defects, said component having optical surfaces, a peripheralsurface and a bulk defined by said optical and peripheral surfaces, arange of inspection of said component including at least one saidoptical surface and said bulk of the component at least in the vicinityof said one optical surface, said method including producing at leastone beam of inspection radiation and directing rays of said at least onebeam onto said peripheral surface at such angles as to enable the raysto travel in said bulk of the component by multiple total internalreflections from said at least one optical surface, providingillumination of each point in said inspection range by set of rays atdifferent angles, and to emerge from said component through saidperipheral surface, and monitoring a radiation scattered by said defectsand emerging from the component through said at least one opticalsurface, thereby identifying said defects.
 2. Method according to claim1, wherein said set of rays is provided in sagittal and meridionalplanes of the component.
 3. Method according to claim 1, wherein therange of inspection of said component includes two optical surfaces andsaid bulk of the component.
 4. Method according to claim 1, wherein theinspection radiation is introduced via component edges.
 5. Methodaccording to claim 1, wherein the inspection radiation is introduced, atleast in part, through a peripheral part of the optical surface adjacentto said component edges.
 6. Method according to claim 1, wherein theinspection radiation consists of a number of beams.
 7. Method accordingto claim 6, wherein said beams of inspection radiation are introducedinto the component at a number of zones along said peripheral surface.8. Method according to claim 1, wherein said at least one beam ofinspection radiation cover an aggregate are of at least 150 degreesalong said peripheral surface.
 9. Method according to claim 1, whereinthe inspection radiation consists of one radiation beam having aring-shaped cross-section in a plane substantially parallel to asagittal plane.
 10. Method according to claim 1, wherein said at leastone beam of inspection radiation is formed and oriented with respect tosaid component substantially in a meridional plane of said component,and scattered substantially in a sagittal plane of said component so asto illuminate at least a part of said peripheral surface of saidcomponent.
 11. Method according to claim 10, wherein the orientation ofthe inspection radiation beams with respect to the component is carriedout by suitably orienting the component.
 12. Method according to claim1, wherein the radiation scattered by the defects and emerging from saidcomponent through said at least one optical surface is monitored byproducing therefrom an image which is analyzed by an appropriate imageprocessing method.
 13. Apparatus for testing optical componentscomprising:means for supporting the component to be tested; illuminationmeans for producing at least one inspection radiation beam; means forconveying said at least one beam to a peripheral surface of thecomponent including optical means for forming said at least one beam ina meridional plane of the component and for orienting said at least onebeam in said meridional plane of the component so as to enable rays ofsaid at least one beam to travel in a bulk of the component by multipletotal internal reflections from at least one optical surface and toemerge from said component through its peripheral surface, and means forscattering said at least one beam in a sagittal plane of the componentabout its peripheral surface so as to provide said radiation with asubstantial divergence in said sagittal plane; means for receivingradiation, if any, emerging from the optical surface; means foranalyzing said radiation, thereby identifying said defects; lightprotection means to avoid a non-controlled illuminating of thecomponent.
 14. Apparatus according to claim 13, wherein the means forsupporting the component to be tested comprises clamps allowingadjustment of the position of the component parallel to its axis. 15.Apparatus according to claim 13, comprising a radiation source forproviding a radiation beam having a ring-shaped cross-section in a planesubstantially parallel to said sagittal plane.
 16. Apparatus accordingto claim 15, further including reflecting means for forming andorienting said beam and directing the beam through said scattering meansto the peripheral surface of the component.
 17. Apparatus according toclaim 15, wherein said radiation source is a laser.
 18. Apparatusaccording to claim 13, wherein said illumination means is adapted toproduce a number of said inspection radiation beams.
 19. Apparatusaccording to claim 13, wherein the illumination means comprises aplurality of radiation sources.
 20. Apparatus according to claim 19,wherein each said plurality of radiation sources is represented bydividing into a number of beams the radiation produced by one radiationsource.
 21. Apparatus according to claim 20, wherein said illuminationmeans include a number of optical fiber bundles adapted to convey saidradiation beams to a plurality of zones about the periphery of thecomponent.
 22. Apparatus according to claim 19, wherein the radiationsources are arranged in a number of rings substantially parallel to saidsagittal plane of the component.
 23. Apparatus according to claim 13,wherein said conveying means include reflection and screening means. 24.Apparatus according to claim 13, wherein said conveying means includesat least one lens and refraction optics.
 25. Apparatus according toclaim 13, wherein the means for receiving radiation comprises a TVcamera.
 26. Apparatus according to claim 13, wherein the means foranalyzing said radiation to identify said defects of the componentcomprise image processing means.